Comparison of seroprevalence from different human populations and regions in China.

A) Comparison of the seropositivity of H9N2 viruses in occupationally exposed populations. The seropositivities among different occupationally exposed populations were significantly different for H9N2 viruses (p = 0.0023 for A/Guangzhou/333/99 (G9) and p = 0.041 for A/quail/Hong Kong/G1/97(G1)). B) Comparison of the seroprevalence of H9N2 viruses in different age groups. Children: aged up to 14; Youth: aged 15–24; Adult: aged 25–59; Elderly: aged over 60. The seroprevalences of H9N2 viruses in different age groups were significantly different (p<0.0001 for both H9N2 viruses). C) Comparison of the seroprevalence of H9N2 antigens in Northern and Southern China. ** indicates p≤0.001.